News flash: Sitting on the couch, eating and watching TV will tend to make you obese.

That may sound a tad obvious. But the authors of a Boston Children’s Hospital study said they’ve gone deeper on the issue, and are trying to find out what kind of screen time is worse.

“It may seem obvious that if you’re sitting at home, watching a lot of TV, you’re not getting a lot of exercise, but it’s much more complicated than that,” said Boston Children’s Hospital scientists David Bickham.

The researchers reached their conclusions with the help of 91 teens, ages 13, 14 and 15. Researchers measured the teens’ height, weight and body mass index, then tracked their use of television, computers, video games and mobile screens for two weeks. The more and more intently children watched TV, researchers found the higher BMI the children were likely to have.

There was no link between video game and computer use and higher BMI levels, researchers said.

“All screen time is not the same,” said Dr. Michael Rich of Children’s Hospital’s Center for Media and Child Health.

“With video games and the computer, your hands are busy, there’s less advertising … TV sets up an environment where food consumption is easy.

“Television is financially supported by advertising, and that advertising is almost never for broccoli,” Rich said.

“Most of the ads are for what’s called high-calorie, nutritionally questionable foods.”

Bickham added, “If you’re engaged with the TV, you’re not paying attention to the food you’re eating, or the cues that your body is giving.”